The prostaglandins are extremely potent substances which produce a wide variety of biological effects, often in the nanomolar to picomolar concentration range. The discovery of two forms of prostaglandin endoperoxide H synthase, isoenzymes PGHS-1 and PGHS-2, that catalyze the oxidation of arachidonic acid leading to prostaglandin biosynthesis has resulted in renewed research to delineate the role of these two isozymes in physiology and pathophysiology. These isozymes have been shown to have different gene regulation and represent distinctly different prostaglandin biosynthesis pathways. The PGHS-1 pathway is expressed constitutively in most cell types. It responds to produce prostaglandins that regulate acute events in vascular homeostasis and also has a role in maintaining normal stomach and renal function. The PGHS-2 pathway involves an induction mechanism which has been linked to inflammation, mitogenesis and ovulation phenomena.
Prostaglandin inhibitors provide therapy for pain, fever, and inflammation, and are useful therapies, for example in the treatment of rheumatoid arthritis and osteoarthritis. The non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen and fenamates inhibit both isozymes. Inhibition of the constitutive enzyme PGHS-1 results in gastrointestinal side effects including ulcers and bleeding and incidence of renal problems with chronic therapy. Inhibitors of the induced isozyme PGHS-2 may provide anti-inflammatory activity without the side effects of PGHS-1 inhibitors.
The problem of side-effects associated with NSAID administration has never completely been solved in the past. Enteric coated tablets and co-administration with misoprostol, a prostaglandin derivative, have been tried in an attempt to minimize stomach toxicity. It would be advantageous to provide compounds which are selective inhibitors of the induced isozyme PGHS-2.
The present invention discloses novel compounds which are selective inhibitors of PGHS-2.